Photographic color printing apparatus



D. R CRAIG ETAL PHOTOGRAPHIC COLOR PRINTING APPARATUS 2 Sheets-Sheet 1 DSIT DSIS 4 INVENTORS DWIN R. CRAIG a FIG FELIX P. TOLOSA gun/M! 3 L- ATTORNEY March 22, 1966 Filed March 1, 1963 March 1966 D. R. CRAIG ETAL PHOTOGRAPHIC COLOR PRINTING APPARATUS 2 Sheets-Sheet 2 Filed March 1, 1963 S R O T N E V N DWIN R. CRAIG 8| FELIX P. TOLOSA BY I E ATTORNEY United States Patent C PHOTOGRAPHIC COLOR PRINTING APPARATUS Dwin R. Craig, Falls Church, and Felix P. Tolosa, Alex- This invention relates to photographic printing apparatus for use with an enlarger in the production of color prints.

In the photographic printing and enlarging of colored images as practiced heretofore, it has been deemed necessary to introduce filters in the path of the exposing light intermediate the light source and the negative as in the case of British Patent 817,277 published on July 29, 1959. By so locating the filters, it has been necessary to construct special enlargers for the purpose or, alternatively, drastically modify existing enlargers. The present inventors have determined through extensive research that since the filters are introduced into the light path for such a relatively brief portion of the exposing operation, they can be introduced into the light path between the lens and the easel so that it becomes relatively simple to install equipment for the purpose in any existing enlarger as an attachment requiring a minimum of modification.

By virtue of this concept, the filters are readily accessible for cleaning and substitution and the equipment can be removed from one enlarger and installed in another quickly and inexpensively.

It has also been found in accordance with the present invention that by introducing the filters into the light path and removing them from the light path in a pivotal fashion rather than linearly, the transition can be much more rapid and the vibration imparted to the enlarger will be appreciably reduced. Moreover, by introducing the filters into the light path by means of springs, and retracting them by means of electromagnets, the travel time during introduction of the filters into the light path is more nearly constant thanwhere the electromagnets are used to move the filters into the light path as occurs in the British patent referred to.

filters imposed in the paths of the photocells. In accordance with the present invention, it has been found that the use of a magenta filter to correspond with thecyan filter produces more faithful prints because the layer of the emulsion which is primarily responsive to red is actually responsive to a substantial amount of blue light as Well. Accordingly, the magenta filter imposed in the path of one of the photoresponsive transducers corresponds to the sensitivity of the particular layer of the emulsion with which it cooperates.

It has also been found to be highly advantageous to expose the photoresponsive transducers to only the central portion of the light to which the printing paper is exposed so as to avoid the effects of the portion of the image lying outside of the center of interest.

' Moreover, for similar reasons, the photoresponsive transducers of the present invention are exposed directly to the light passing through the printing paper so as to avoid the adverse effects of a reflector such as that used in the British patent referred to for averaging the light transmitted to the photocells of that patent.

The present invention also provides for compensation for subject failure and density failure by the provision of adjusting means whereby the intensity response of the photo-responsive transducers can be adjusted individually and collectively and whereby the capacitors of the integrating circuits of the photoresponsive transducers can have their initial voltage values adjusted individually.

It is among the objects of the present invention to provide photographic printing apparatus for an enlarger having an easel, a head suporting a source for directing light on the easel, a lens in the path of the light between the source and easel, and a negative carrier in the path between the source and lens, comprising means supporting a plurality of subtractive filters between the lens and easel, means for shifting each of the filters individually into and from the path, a plurality of photoresponsive transducers in the path beyond the easel each having a color response characteristic which corresponds with one color sensitive layer of a multicolor printing element, and circuit means interconnecting each photoresponsive transducer with one of the shifting means.

The lens and filters are preferably detachably mounted on the head and the circuit means preferably includes an integrating circuit between each photoresponsive transducer and its related shifting means. The shifting means preferably includes electromagnets for retracting the filters respectively from the path and the filters are preferably pivotally mounted for movement into and from the path. Three subtractive filters are preferably employed and shifted in response to three photoresponsive transducers respectively. The circuit means preferably includes means for simultaneously adjusting the intensity response of all of the photoresponsive transducers and means for individually adjusting the intensity response of each of the transducers. The circuit means preferably includes an integrating capacitor in circuit with each photoresponsive transducer together with means for applying an initial voltage to each capacitor and means for varying the initial voltage applied to each capacitor.

The color response characteristics of the electroresponsive transducers are preferably blue, green and magenta corresponding respectively to filters between the lens and easel which are yellow, magenta and cyan respectively. The easel preferably provides a window for transmitting light from the source, through a multicolor printing element, to the photoresponsive transducers, which window has dimensions smaller than those of the printing element itself. Springs are preferably employed to normally impose the filters in the light path, and the circuit means preferably includes means for retracting the filters from the path, energizing the light source and simultaneously inactivating the photoresponsive transducers.

A more complete understanding of the invention will follow from a description of the accompanying drawings wherein:

FIG. 1 is a fragmentary perspective view depicting photographic printing apparatus according to the present invention applied to existing enlarging apparatus;

FIG. 2 is a'schematic view of the apparatus associated with an enlarger;

FIG. 3 "is a bottom plan view of the electromagnetically retracted filter assembly interposed between the lens and the easel;

FIG. 4 is a sectional elevation taken along line 4-4 of FIG. 3; and I 1 FIG. 5 is a circuit diagram of the apparatus.

Referring to the drawings, there is depicted an enlarger having a base a column 12, a bellows 14, and a lens 16 mounted on a conventional lens board 18. Above the lens as shown in FIG. 2, but absent from FIG. 1, there is provided a negative carrier 20, condensing lenses 22, and a light source 24. Depending from the lens board 18 by means of suitable posts 26 terminating in a ring 28 is a housing 30 containing a filter and solenoid assembly illustrated in more detail in FIGS. 3 and 4. The ring 28 and housing 30 may be detachably connected by means of suitable latches, not shown, to facilitate disassembly.

An easel assembly 32 is supported by the base 10 and provides a holder 34 for a sheet of multicolor printing paper 36 upon which light from the source 24 is focused for the production of a color print. The easel assembly 32 includes a housing 38 in whose top wall there is provided a window 40 of smaller dimensions than the printing paper 36 to be used so that the photoresponsive transducers or photocells V1, V2 and V3 contained within the housing 38 will receive light only from the central portion of the image produced on the printing paper so as to avoid the efiects of the portion of the image lying outside of the center of interest of the picture The photosensitive transducers V1, V2 and V3 have their respective sensitivities controlled by means of variable resistors R1, R2 and R3, as will become evident by inspection of the circuit diagram of FIG. 5, the outputs of these photoresponsive transducers being connected to their respective integrating circuits, thyratron tubes, relays and other controls contained within a housing 42. The photo-responsive transducers have their circuits connected by means of leads 44, 46 and 48 combined in a cable 50 to their respective integrating circuits containing capacitors C5, C6 and C7. The control knobs R35, R36 and R37 mounted on the housing 42 determine the initial voltages applied to the capacitors C5, C6 and C7 respectively, so that the operator can make adjustments to desired values where he observes that the scene to be printed should be predominantly one color rather than averaging out to a gray. Where less of a given color is desired, the corresponding knob will be turned counterclockwise, and similarly, where more of that color is desired, the knob will be moved in a clockwise direction. The housing 42 also carries a knob for simultaneously controlling the sensitivity of all of the photo-responsive transducers, designated R42, which also identifies the variable resistor shown in the circuit digram of FIG. 5. The panel of the housing 42 also carries the switch S2 which is the compose switch having one position in which the light source is energized, the filters removed from the light path and the photoresponsive transducers deenergized. In its other position,

- the switch S2 will cause the light source to be deenergized,

will permit the filters to move into the light path and will permit the photoresponsive transducers to be energized. The push-button switch S3 on the panel of the housing 42 is the expose switch which is actuated when the equipment is ready to expose a sheet of printing paper supported on the easel. The indicators DS15, D516 and D817 mounted on the panel of the housing 42 represent neon lamps which, when illuminated will indicate that their respective filters have been removed from the light path by their solenoids. The power switch S1 shown in FIG. 5 does not appear in FIGS. 1 and 2 because it is mounted on the rear surface of the housing 42. However, the power switch is in circuit with the line cord 52 terminating in a plug 54.

Mounted within the housing 30 are three rotary solenoids E1, E2 and E3 such as those described in Catalog A262 of Ledex Inc., 123 Webster St., Dayton 2, Ohio, No. H-lO79-037. These solenoids are equipped with springs which project their respective filters 56, 58 and 60 to the dotted line positions depicted in FIG. 3, the full line positions of the filters being achieved by energization of the respective solenoids. By the use of rotary solenoids of this type, vibration is reduced so that undesired movement of the enlarger head is avoided and blurring of the print will not occur. As the filters are biased by their springs into the light path, they engage a resilient bumper 64 so as to further reduce vibration and movement of the enlarger head, and as the filters are withdrawn from the light path by energization of their respective solenoids, they engage another resilient bumper 62 for the same purpose. The solenoids E1, E2 and B3 are connected by means of leads 66, 68 and 70 respectively, combined in a cable 72 to their respective relay terminals contained within the housing 42.

The photoresponsive transducers V1, V2 and V3 have imposed in their respective light paths magenta, green and blue filters 72, 74 and 76 whose circuits respectively control the solenoids E1, E2 and E3 which operate the filters 56, 58 and 60 which are respectively cyan, magenta and yellow.

The light source 24 is supplied with current through a cable 78 extending from the housing 42 as depicted in FIGS. 1, 2 and 5.

In operation, the power switch S1 will be closed whereupon the photosenstive transducers Will cause their thyratrons V4, V5 and V6 to fire, energizing their relays K1, K2 and K3 to shift the contacts of these relays from the positions shown to their opposite positions. A negative 80 to be printed will be in position. in the negative carrier 20. The operator will then throw the switch S2 to its closed or compose position so as to energize the relay K4 and shift its contacts from the positions shown to their opposite positions. Under these conditions the relay K5 is also energized by the contact K4? so that its contacts K5A and KSB will energize the light source 24. The contacts K1C, K2B and K3C will have moved to their right hand positions so as to deenergize the photo-responsive transducers V1, V2 and V3, At the same time, the solenoids E1, E2 and E3 will be energized through the contacts K4A, K4B and K4C to retract the filters 56, 58 and 60 from the light path. Under these conditions, the operator can focus the image on the easel and adjust such of the resistors R1, R2, R3, R35, R36, R37 and/ or R42 as may be required for the particular negative and print to be produced. The operator will then restore the switch S2 to its open position as depicted in FIG. 5, place the printing paper on the easel and operate the expose switch S3 to momentarily open it and then close it so as to energize the light source and photoresponsive transducers and retract the filters by means of their solenoids E1, E2 and E3. Then, as each photoresponsive transducer and its respective integrating circuit senses a predetermined amount of light of its assigned color, its respective relay K1, K2 and K3 will be actuated to deenergize the respective solenoids E1, E2 and E3 to permit the respective filters 56, 58 and 60 to be introduced into the light path by means of the springs with which the solenoids are equipped. As each of the relays K1, K2 and K3 becomes energized, the contacts KlB, K20, and K3B respectively, will be shifted from the positions depicted in FIG. 5 to their opened or lowered positions so that when the last of the three has been shifted, the relay K5 will be deenergized and the contacts KSA and K5B will resume their open positions depicted in FIG. 5 to open the circuit of the light source 24.

As previously indicated, the resistors R35, R36 and R37 adjust the initial voltage applied to the capacitors C5, C6 and C7 respectively, thus determining the amount of charge to be integrated in order to actuate the respective thyratrons V4, V5 and V6.

Whereas the foregoing description has been directed to a specific embodiment of the invention, the arrangement shown and described can be modified within the scope of the appended claims.

We claim:

1. Photographic printing apparatus for an enlarger having an easel, a head supporting a source for directing light on said easel, a lens in the path of said light between said source and easel, and a negative carrier in said path between said source and lens, comprising means supporting a plurality of subtractive filters between said lens and easel, means for shifting each of said filters individually into and from said path, a plurality of photoresponsive transducers in said path beyond said easel each having a color response characteristic which corresponds with one color sensitive layer of a multicolor printing element, and circuit means interconnecting each photoresponsive transducer with one of said shifting means, said subtractive filters being yellow, magenta, and cyan respectively and said photoresponsive transducers controlling the shifting of said subtractive filters being sensitive to blue, green and magenta light components respectively.

2. Photographic printing apparatus according to claim 1 wherein said lens and filters are detachably mounted on said head.

3. Photographic printing apparatus according to claim 1 wherein said circuit means includes an integrating circuit between each photoresponsive transducer and its related shifting means.

4. Photographic printing apparatus according to claim 1 wherein said shifting means includes electromagnets for retracting said filters respectively from said path.

5. Photographic printing apparatus according to claim 1 wherein said filters are pivotally mounted for movement into and from said path.

6. Photographic printing apparatus according to claim 1 wherein three subtractive filters are shifted in response to three photoresponsive transducers respectively.

7. Photographic printing apparatus according to claim 1 wherein said circuit means includes means for simultaneously adjusting the intensity response of all of said photoresponsive transducers. 8. Photographic printing apparatus according to claim 1 wherein said circuit means includes an integrating capacitor in circuit with each said photoresponsive transducer, means for applying an initial voltage to each capacitor, and means for varying the initial voltage applied to each capacitor.

9. Photographic printing apparatus according to claim 1 wherein the color response characteristics of said photoresponsive transducers are blue, green and magenta respectively.

10. Photographic printing apparatus according to claim 1 wherein said easel provides a window for transmitting light from said source, through a multicolor printing element, to said photoresponsive transducers, said window having dimensions smaller than those of said printing element.

11. Photographic printing apparatus according to claim 1 wherein springs normally impose said filters in the light path.

12. Photographic printing apparatus according to claim 1 wherein said circuit means includes means for individually adjusting the intensity response of each of said photoresponsive transducers.

13. Photographic printing apparatus according to claim 1 wherein said circuit means includes means for retracting said filters from said path, energizing said light source and simultaneously inactivating said photoresponsive transducers.

References Cited by the Examiner UNITED STATES PATENTS 3,062,096 11/1962 Brown 88-24 FOREIGN PATENTS 817,277 7/1959 Great Britain.

NORTON ANSHER, Primary Examiner. R. A. WINTERCORN, Assistant Examiner. 

1. PHOTOGRAPHIC PRINTING APPARATUS FOR AN ENLARGER HAVING AN EASEL, A HEAD SUPPORTING A SOURCE FOR DIRECTING LIGHT ON SAID EASEL, A LENS IN THE PATH OF SAID LIGHT BETWEEN SAID SOURCE AND EASEL, AND A NEGATIVE CARRIER IN SAID PATH BETWEEN SAID SOURCE AND LENS, COMPRISING MEANS SUPPORTING A PLURALITY OF SUBTRACTIVE FILTERS BETWEEN SAID LENS AND EASEL, MEANS FOR SHIFTING EACH OF SAID FILTERS INDIVIDUALLY INTO AND FROM SAID PATH, A PLURALITY OF PHOTORESPONSIVE TRANSDUCERS IN SAID PATH BEYOND SAID EASEL EACH HAVING A COLOR RESPONSE CHARACTERISTIC WHICH CORRESPONDS WITH ONE COLOR SENSITIVE LAYER OF A MULTICOLOR PRINTING ELEMENT, AND CIRCUIT MEANS INTERCONNECTING EACH PHOTORESPONSIVE TRANSDUCER WITH ONE OF SAID SHIFTING MEANS, SAID SUBTRACTIVE FILTERS BEING YELLOW, MAGENTA, AND CAYN RESPECTIVELY AND SAID PHOTORESPONSIVE TRANSDUCERS CONTROLLING THE SHIFTING OF SAID SUBTRACTIVE FILTERS BEING SENSITIVE TO BLUE, GREEN AND MAGENTA LIGHT COMPONENTS RESPECTIVELY. 